<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body{
            position: relative;
        }
        div{
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%,-50%);
        }
        .box1{
            width: 800px;
            height: 800px;
            background-color: lightblue;
        }
        .box2{
            width: 500px;
            height: 500px;
            background-color: lightpink;
        }
        .box3{
            width: 200px;
            height: 200px;
            background-color: lightgreen;
        }
    </style>
</head>
<body>
    <div class="box1">
        <div class="box2">
            <div class="box3"></div>
        </div>
    </div>
</body>
</html>